Bags of synthetic fabric comprising a base and four vertical sides, in general two long sides and two short sides, are well known, the document EP0691286 (B1) can be cited by way of simple reference, but a multitude of documents could easily be cited.
In theory, or when they are drawn on paper, these bags stand up perfectly, their sides are properly vertical and taut and the mouth of the bag remains open and properly deployed to receive what one wishes to transport in the bag.
In practice, the sides of a real bag are much less obedient than on paper such that they tend to lean over, then to lie towards the interior of the bag, sometimes candling with their counterpart in the manner of a parachute which fails to open properly, but in all cases this results in the mouth of the bag closing in a more or less surreptitious manner.
Who has not had this experience that, having to hold an object or a load with both hands (a shovelful of sand or an armful of dead leaves) so as to place it into a bag, one does not manage to open the mouth of the bag and one is reduced to asking for the assistance of another person to hold the bag open.
Of course, the major difference between a bag and a rigid box is that the bag can be easily folded, that the space which it occupies once folded is minimal in comparison with its deployed effective volume, and that it remains infinitely lighter than a rigid container. It is not a question of abandoning these traditional advantages of the bag by having recourse to some form of internal or external chassis to remedy the above-mentioned disadvantages. The exercise wishes for the improvement to result exclusively from a modification of the properties of the pieces of fabric, even their arrangement.